Wireless communication systems are widely deployed to provide various communication services such as voice, video, packet data, messaging, broadcast, etc. These wireless systems may be multiple-access systems capable of supporting multiple users by sharing the available system resources, e.g., time, frequency, power. Examples of such multiple-access systems include Code Division Multiple Access (CDMA) systems, Time Division Multiple Access (TDMA) systems, Frequency Division Multiple Access (FDMA) systems, Orthogonal FDMA (OFDMA) systems, and Single-Carrier FDMA (SC-FDMA) systems.
A wireless communication system may include a number of base stations that can support communication for a number of mobile terminals. The system may support operation on multiple carriers. Each carrier may be associated with a particular center frequency and a particular bandwidth. Each carrier may carry pilot and overhead information to support operation on the carrier. Each carrier may also carry data for terminals operating on the carrier. Some transmissions between a terminal and a base station may cause interference to, and may also observe interference from, other transmissions in the communication system. The interference may adversely impact the performance of all affected base stations.
Further, traffic load in the wireless communication system can impede performance of the system. Loads vary dynamically, with users coming to and leaving from the system or moving within the system over short periods of time. Further, traffic demands of users vary in time, e.g., with a user inducing a large load for a data download, but then no or little loading after that. Also, loads within the system are non-uniform. Different users may have different demands and thus induce different loading on the system. For example, one user may have a large data download requiring significant system resources while another user may have a small data demand requiring few system resources. Higher load levels typically increase interference, reducing performance quality and efficiency.
Referring to FIG. 7, a plot 130 shows a sequence of sub-packets transmitted over time from a wireless network access terminal (AT) to base transceiver stations (BTSs). As shown, four sub-packets 132, 134, 136, 138 are transmitted over time, with each sub-packet containing four slots, and there being eight slots in between each pair of sub-packets from the end of one sub-packet to the beginning of the next sub-packet. The eight-slot gaps 140 between the packets 132, 134, 136, 138 provide time for a BTS to acknowledge decoding of the sub-packet. A termination goal (TG) or termination target can be established for the AT as a goal for the amount of slots to be transmitted before decoding by the BTS. As indicated here, TG 4, TG 8, TG 12, TG 16 goals correspond to the end of transmission of the sub-packets 132, 134, 136, 138, respectively. The termination goal represents the amount of slots to be transmitted such that the percentage chance of decoding after the transmission of that number of slots is 99% or greater. Thus, with a termination goal TG 4, after transmission of the sub-packet 132, less than 1% of the time the sub-packet 132 will not be decoded by the BTS. For TG 16, a typical profile of decoding percentages is 10% being decoded after transmission of the sub-packet 132, 40% decode success after transmission of the sub-packet 134, another 40% successful decode after transmission of the sub-packet 136, and another 9% successful decode after transmission of the sub-packet 138. This, however, is an exemplary profile of decodes success rate, and other profiles may exist. The decode success profile will vary from channel to channel. The likelihood of successful decode depends on, among other things, the transmit power of the sub-packets 132, 134, 136, 138 from the AT.
As the termination goal number increases, the capacity from the AT increases and latency also increases. The converse is true as the termination goal number decreases. Thus, a termination goal of TG 16 has a higher capacity and higher latency than termination goals TG 4 or TG 8. A termination goal of TG 16 is referred to a high-capacity, or a HiCap termination goal while termination goals of TG 4 or TG 8 are often referred to as low-latency, or LoLat, termination goals.
In 1xEV-DO Rev-A systems, the peak data transmission rate from ATs is about 1.8 Mbps. In Rev-A, packet sizes range from 128 bits to 12 Kbits. With a packet size of 128 bits and a termination goal of TG 16, the data rate is 4.8 Kbits while with a packet size of 12 Kbits the data rate is 460 Kbits. To increase the data rate beyond 460 Kbps, the termination goal can be lowered. If the termination goal is lowered to TG 4, the data rate increases to about 1.8 Mbps. The increase of data rate comes, however, through an increase in transmission energy from the AT which results in higher interference and a reduction in capacity.